unitfile-parser
v1.0.4
Published
Parse systemd unit files
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unitfile-parser
This is a small utility library to parse systemd unitfiles to and from JavaScript data structures. Three formats are available:
string
, which is the representation inside of a unit file,ast
, which is a JS object representation of the parser AST, including comments,data
, which is a normalized representation of the data, useful to do general computing. It has the following format:
{
title: String,
settings: {
[key:String]: String|String[],
}
}[]
Conversions are available in all directions between these formats, with the only external dependency being chevrotain
.
This package does not know or check whether the logic of a unit file is correct (e.g. are you using the correct names for options, etc.), it only knows what the syntax is supposed to be.
Usage
For most usecases, you'll only need two functions: stringToData
and dataToString
:
import { readFile, writeFile } from 'fs/promises';
import { stringToData, dataToString } from 'unitfile-parser';
(async () => {
const unitFilePath = '~/.config/systemd/user/xsettingsd.service';
// Read the current file from disk
const fileContents = await readFile(unitFilePath);
// Transform it to a useful data structure
const unit = stringToData(fileContents);
// Change it around
const transformedUnit = doSomeTransformation(unit);
// Transform the changed unit back to a string
const newFileContents = dataToString(transformedUnit);
// Write the changed file back to disk
await writeFile(unitFilePath, newFileContents);
})();
API
This package is written for esm5 and above, providing only JS modules (.mjs
files) to work with.
stringToAst(input: String): Object
Convert a unit file string to a JS AST.
import { readFile } from 'fs/promises';
import { stringToAst } from 'unitfile-parser';
readFile('~/.config/systemd/user/xsettingsd.service')
.then(fileContents => {
const ast = stringToAst(fileContents);
console.log(ast);
});
stringToData(input: String): Array
Convert a unit file string to a normalized representation. This is equivalent to the following:
const data = astToData(stringToAst(string));
astToData(ast: Object): Array
Convert the parser ast to a normalized representation.
astToString(ast: Object): String
Convert an ast to a valid unit file string.
import { writeFile } from 'fs/promises';
import { astToString } from 'unitfile-parser';
const ast = // some ast here
const unitFile = astToString(ast);
writeFile('~/.config/systemd/user/xsettingsd.service', unitFile);
dataToAst(data: Array): Object
Convert the normalized JS representation to the parser ast.
dataToString(data: Array): String
Convert the normalized JS representation to a valid unit file string. This is equivalent to the following:
const string = astToString(dataToAst(data));
Lexer
Constructor for a lexer that extends the chevrotain Lexer.
Parser
Constructor for a parser that extends the chevrotain CSTParser.
visitorCreator(parser: Parser): ICSTVisitor
Function that takes a parser and returns a visitor for that parser that would normalize the ast to the abovementioned data format.
Motivation
There already is a systemd-unitfile
package on npm, but it is unmaintained and has some bad behaviour, like not recognizing multiline values.